Magnetic tape is often used for storage and retrieval of data, and comes in many widths, lengths and formats. Magnetic tape remains an economical medium for storing large amounts of data. For example, magnetic tape cartridges or spools of magnetic tape are often used to back up large amounts of data for computing centers and the like. Magnetic tape cartridges also find application in the backup of data stored on smaller computers such as workstations, desktop computers and laptop computers. In addition, magnetic tape is commonly used in video recording, including both analog and digital video recording.
Video recording on magnetic tape typically uses helical scanning, in which the magnetic tape is fed past a rotating drum. The rotating drum includes one or more contact areas that protrude from the drum to contact the magnetic tape. The contact areas define magnetic gaps that facilitate data recording on the magnetic tape and the reading of data stored on the magnetic tape. The motion of the magnetic gap(s) on the rotating drum are typically much faster than the lateral movement of the magnetic tape past the drum. For example, the motion of the magnetic gaps on the drum may be in the range of approximately 1–20 meters per second, whereas the motion of the magnetic tape past the drum may be in the range of approximately 1–20 centimeters per second.
In helical scanning, such as that used in video recording, the rotating drum rotates at an offset angle relative to motion of the tape, which causes helical data tracks to be formed on the magnetic tape as the tape passes by the rotating drum. Moreover, the rotating drum creates an air interface between the tape and the drum in the regions of the drum that do not correspond to the contact area(s). Thus, the tape essentially “flies” relative to the rotating drum, and is contacted only by the contact areas(s) that protrude from the drum.
Linear scanning refers to techniques in which linear tape is fed past a non-rotating head. In contrast to helical scanning in which a rotating drum includes a protruding contact area defining a magnetic gap, in linear scanning the magnetic gap is positioned at a generally fixed location associated with a non-rotating magnetic head, and the linear tape feeds past the magnetic gap of the non-rotating magnetic head. Accordingly, data tracks on linear tape are typically parallel to the length of the tape. In linear scanning, the magnetic tape typically feeds past a non-rotating head at a tape speed of approximately 1–20 meters per second.
Conventional head designs for linear scanning are generally more aggressive than heads used in helical scanning, particularly in terms of the size of the contact area between the head and the tape. In addition, in linear scanning the linear tape typically does not fly over any structure prior to contact with the linear head. Instead, linear tape is typically fed into direct contact with a relatively large contact area that defines the magnetic head. In addition, sharp corners are often used on conventional linear heads to improve the intimate contact between the magnetic head and the magnetic tape. This aggressive contact design of linear heads, however, generally limits the use of fragile tape media in linear scanning systems.